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  • 1
    Electronic Resource
    Electronic Resource
    The Thermally and Photochemically Induced Ring Opening of cis-3,4-Dichlorocyclobutene and trans-3,4-Dichlorocyclobutene: New Insights from a Matrix-Spectroscopic Study (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2063-2072 
    Details
    ISSN: 1434-193X
    Keywords: Matrix isolation ; Ring opening ; Flash pyrolysis ; Photochemistry ; Cyclobutenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced ring opening of 1 and 5 proceeds with high stereospecifity in a conrotatory fashion in agreement with the Woodward-Hoffmann rules. Upon flash pyrolysis of 1 the matrix-isolated (Xe, 12 K) products 2a and 2b were found, whereas the corresponding reaction of 5 yielded 3a and 3b. The s-cis conformers 2b and 3b were identified for the first time by comparison of the experimental and calculated (BLYP-6-311G*) IR absorptions. A non-stereospecific photochemical reaction could be observed if matrix-isolated (Ar or Xe, 12 K) 1 was excited directly with λ = 193 nm. Products of the allowed disrotatory pathway as well as those of the forbidden conrotatory reaction were found, a behaviour that corresponds with the known photochemistry of cyclobutenes. A surprising reaction was found if 1 and 5 were irradiated in a xenon matrix with λ 〉 270 nm. The precursors, which were photostable in an argon matrix, opened the ring in a conrotatory fashion, the expected pathway for a thermal reaction. In this case the light is absorbed by the solid xenon in a cooperative process with the precursor molecules. A detailed discussion of the possible energy transfer mechanisms is given. Most probably, a hot ground-state reaction of vibrationally excited 1 and 5 occurs, although the reaction of the radical cations cannot be excluded.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Isofulminic Acid - Phantom or Reality?Dedicated to Professor Dieter Seebach on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2505-2517 
    Details
    ISSN: 0947-3440
    Keywords: Matrix isolation ; Photochemistry ; CHNO isomers ; Hydrogen-bonded complexes ; Density functional calculations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex photochemistry of matrix-isolated dihaloformoximes 8a, 8b, and 8c, which are transformed upon irradiation into the new hydrogen-bonded complexes HalCN…HOHal 10a-c′, identified by their IR spectra, has been unveiled. An earlier assignment of the experimental IR absorptions to isofulminic acid HONC (4) must be withdrawn. A competitive reaction to the formation of complexes 10a-c′ produces the hydrogen-bonded complexes HalNCO/HHal 12a-c′, which can be regarded as intermediates on the photochemical pathway to the final product isocyanic acid HNCO (1), and are tentatively identified by their IR absorptions. Our findings are supported by deuteration experiments and theoretical calculations using the density functional method BLYP/6-311G*.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971213
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  • 3
    Electronic Resource
    Electronic Resource
    Matrix-Isolation of Iodine Superoxide and Iodine Dioxide (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 179-181 
    Details
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Pyrolysis ; Photochemistry ; Iodine compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash pyrolysis of a gas mixture containing iodine, oxygen and argon yields the hitherto unknown iodine superoxide, which can be identified by its UV absorption (λ max= 254 nm) after trapping the pyrolysate at 12 K. Irradiation converts iodine superoxide into iodine dioxide, identified by its IR and UV spectra.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300207
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    Paper (German National Licenses)
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